Many types of useful linear fluorocarbon acids are known, such as trifluoromethanesulfonic acid, trifluoroacetic acid, and perfluoroalkanedisulfonimides of the formula RSO.sub.2 NHSO.sub.2 R, where R is a monovalent perfluoroalkyl group. German Patent No. 22 39 817 discloses the preparation of perfluoroalkanedisulfonimides and their use as esterification catalysts, and U.S. Pat. No. 4,031,036 discloses the use of perfluoroaliphaticdisulfonimides as catalysts for the polymerization of cationically-sensitive monomers. In contrast to the linear fluorocarbon acids, few cyclic fluorocarbon acids are known. Henne et al, J.A.C.S. 73, 1103 (1951) have disclosed the cyclization of perfluorosuccinamide and perfluoroglutaramide to perfluorosuccinimide and perfluoroglutarimide, respectively.
The processes of formation of cyclic compounds by ring closure are generally known to be unpredictable because of ring instability, inability of functional groups to undergo ring closure, or decomposition of functional groups during the process of ring formation. For example, alkanedisulfonyl halides give linear olefinic sulfonamides on reaction with ammonia, e.g., 1,2-ethanedisulfonyl chloride yields CH.sub.2 .dbd.CHSO.sub.2 NH.sub.2 on reaction with ammonia, see "The Organic Chemistry of Sulfur" by C. M. Suter, pp. 168-169, John Wiley and Sons, Inc., New York (1948).